[Python-Dev] Removing callable() from the stdlib

Guido van Rossum guido at python.org
Fri Mar 28 20:58:03 CET 2008

On Fri, Mar 28, 2008 at 10:51 AM, Collin Winter <collinw at gmail.com> wrote:
> I've been running 2to3's fix_callable over 2.6's stdlib to remove -3
>  warnings due to callable() usage; 2to3 replaces callable(x) with
>  has_attr(x, "__call__"). Unfortunately, this breaks code that wants to
>  run callable() on old-style classes (like test_builtin), because
>  old-style classes don't have a __call__ attribute (new-style classes
>  do, however).
>  How should this be handled? I'm tempted to just add __call__ to
>  old-style classes for 2.6, but Neal Norwitz thought that might break
>  some user code. Any other thoughts?

I don't see how this would break user code, as long as the __call__
shows up for the *class* but not for the *instance*, and as long as it
doesn't break users overriding __call__ in a classic class to make the
instances callable.

--Guido van Rossum (home page: http://www.python.org/~guido/)

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